1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94 33.\" $FreeBSD$ 34.\" 35.Dd June 18, 2001 36.Dt SYSCONF 3 37.Os 38.Sh NAME 39.Nm sysconf 40.Nd get configurable system variables 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft long 46.Fn sysconf "int name" 47.Sh DESCRIPTION 48This interface is defined by 49.St -p1003.1-88 . 50A far more complete interface is available using 51.Xr sysctl 3 . 52.Pp 53The 54.Fn sysconf 55function provides a method for applications to determine the current 56value of a configurable system limit or option variable. 57The 58.Fa name 59argument specifies the system variable to be queried. 60Symbolic constants for each name value are found in the include file 61.Aq Pa unistd.h . 62Shell programmers who need access to these parameters should use the 63.Xr getconf 1 64utility. 65.Pp 66The available values are as follows: 67.Pp 68.Bl -tag -width 6n 69.Pp 70.It Li _SC_ARG_MAX 71The maximum bytes of argument to 72.Xr execve 2 . 73.It Li _SC_CHILD_MAX 74The maximum number of simultaneous processes per user id. 75.It Li _SC_CLK_TCK 76The frequency of the statistics clock in ticks per second. 77.It Li _SC_IOV_MAX 78The maximum number of elements in the I/O vector used by 79.Xr readv 2 , 80.Xr writev 2 , 81.Xr recvmsg 2 , 82and 83.Xr sendmsg 2 . 84.It Li _SC_NGROUPS_MAX 85The maximum number of supplemental groups. 86.It Li _SC_OPEN_MAX 87The maximum number of open files per user id. 88.It Li _SC_STREAM_MAX 89The minimum maximum number of streams that a process may have open 90at any one time. 91.It Li _SC_TZNAME_MAX 92The minimum maximum number of types supported for the name of a 93timezone. 94.It Li _SC_JOB_CONTROL 95Return 1 if job control is available on this system, otherwise \-1. 96.It Li _SC_SAVED_IDS 97Returns 1 if saved set-group and saved set-user ID is available, 98otherwise \-1. 99.It Li _SC_VERSION 100The version of 101.St -p1003.1 102with which the system 103attempts to comply. 104.It Li _SC_BC_BASE_MAX 105The maximum ibase/obase values in the 106.Xr bc 1 107utility. 108.It Li _SC_BC_DIM_MAX 109The maximum array size in the 110.Xr bc 1 111utility. 112.It Li _SC_BC_SCALE_MAX 113The maximum scale value in the 114.Xr bc 1 115utility. 116.It Li _SC_BC_STRING_MAX 117The maximum string length in the 118.Xr bc 1 119utility. 120.It Li _SC_COLL_WEIGHTS_MAX 121The maximum number of weights that can be assigned to any entry of 122the LC_COLLATE order keyword in the locale definition file. 123.It Li _SC_EXPR_NEST_MAX 124The maximum number of expressions that can be nested within 125parenthesis by the 126.Xr expr 1 127utility. 128.It Li _SC_LINE_MAX 129The maximum length in bytes of a text-processing utility's input 130line. 131.It Li _SC_RE_DUP_MAX 132The maximum number of repeated occurrences of a regular expression 133permitted when using interval notation. 134.It Li _SC_2_VERSION 135The version of 136.St -p1003.2 137with which the system attempts to comply. 138.It Li _SC_2_C_BIND 139Return 1 if the system's C-language development facilities support the 140C-Language Bindings Option, otherwise \-1. 141.It Li _SC_2_C_DEV 142Return 1 if the system supports the C-Language Development Utilities Option, 143otherwise \-1. 144.It Li _SC_2_CHAR_TERM 145Return 1 if the system supports at least one terminal type capable of 146all operations described in 147.St -p1003.2 , 148otherwise \-1. 149.It Li _SC_2_FORT_DEV 150Return 1 if the system supports the FORTRAN Development Utilities Option, 151otherwise \-1. 152.It Li _SC_2_FORT_RUN 153Return 1 if the system supports the FORTRAN Runtime Utilities Option, 154otherwise \-1. 155.It Li _SC_2_LOCALEDEF 156Return 1 if the system supports the creation of locales, otherwise \-1. 157.It Li _SC_2_SW_DEV 158Return 1 if the system supports the Software Development Utilities Option, 159otherwise \-1. 160.It Li _SC_2_UPE 161Return 1 if the system supports the User Portability Utilities Option, 162otherwise \-1. 163.El 164.Sh RETURN VALUES 165If the call to 166.Fn sysconf 167is not successful, \-1 is returned and 168.Va errno 169is set appropriately. 170Otherwise, if the variable is associated with functionality that is not 171supported, \-1 is returned and 172.Va errno 173is not modified. 174Otherwise, the current variable value is returned. 175.Sh ERRORS 176The 177.Fn sysconf 178function may fail and set 179.Va errno 180for any of the errors specified for the library function 181.Xr sysctl 3 . 182In addition, the following error may be reported: 183.Bl -tag -width Er 184.It Bq Er EINVAL 185The value of the 186.Fa name 187argument is invalid. 188.El 189.Sh SEE ALSO 190.Xr getconf 1 , 191.Xr pathconf 2 , 192.Xr confstr 3 , 193.Xr sysctl 3 194.Sh BUGS 195The value for _SC_STREAM_MAX is a minimum maximum, and required to be 196the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously 197small and misleading number. 198.Sh STANDARDS 199Except for the fact that values returned by 200.Fn sysconf 201may change over the lifetime of the calling process, 202this function conforms to 203.St -p1003.1-88 . 204.Sh HISTORY 205The 206.Fn sysconf 207function first appeared in 208.Bx 4.4 . 209